Basic SimpleXML usage

Many examples in this reference require an XML string. Instead of
repeating this string in every example, we put it into a file which
we include in each example. This included file is shown in the
following example section. Alternatively, you could create an XML
document and read it with simplexml_load_file().

The simplicity of SimpleXML appears most clearly when one extracts
a string or number from a basic XML document.

Example #2 Getting <plot>

<?phpinclude 'example.php';

$movies = new SimpleXMLElement($xmlstr);

echo $movies->movie[0]->plot;?>

The above example will output:

So, this language. It's like, a programming language. Or is it a
scripting language? All is revealed in this thrilling horror spoof
of a documentary.

Accessing elements within an XML document that contain characters not permitted under
PHP's naming convention (e.g. the hyphen) can be accomplished by encapsulating the
element name within braces and the apostrophe.

Example #3 Getting <line>

<?phpinclude 'example.php';

$movies = new SimpleXMLElement($xmlstr);

echo $movies->movie->{'great-lines'}->line;?>

The above example will output:

PHP solves all my web problems

Example #4 Accessing non-unique elements in SimpleXML

When multiple instances of an element exist as children of
a single parent element, normal iteration techniques apply.

<?phpinclude 'example.php';

$movies = new SimpleXMLElement($xmlstr);

/* For each <character> node, we echo a separate <name>. */foreach ($movies->movie->characters->character as $character) { echo $character->name, ' played by ', $character->actor, PHP_EOL;}

?>

The above example will output:

Ms. Coder played by Onlivia Actora
Mr. Coder played by El ActÓr

Note:

Properties ($movies->movie in previous example) are not
arrays. They are iterable and
accessible objects.

Example #5 Using attributes

So far, we have only covered the work of reading element names
and their values. SimpleXML can also access element attributes.
Access attributes of an element just as you would elements
of an array.

There is a common "trick" often proposed to convert a SimpleXML object to an array, by running it through json_encode() and then json_decode(). I'd like to explain why this is a bad idea.

Most simply, because the whole point of SimpleXML is to be easier to use and more powerful than a plain array. For instance, you can write <?php $foo->bar->baz['bing'] ?> and it means the same thing as <?php $foo->bar[0]->baz[0]['bing'] ?>, regardless of how many bar or baz elements there are in the XML; and if you write <?php (string)$foo->bar[0]->baz[0] ?> you get all the string content of that node - including CDATA sections - regardless of whether it also has child elements or attributes. You also have access to namespace information, the ability to make simple edits to the XML, and even the ability to "import" into a DOM object, for much more powerful manipulation. All of this is lost by turning the object into an array rather than reading understanding the examples on this page.

Additionally, because it is not designed for this purpose, the conversion to JSON and back will actually lose information in some situations. For instance, any elements or attributes in a namespace will simply be discarded, and any text content will be discarded if an element also has children or attributes. Sometimes, this won't matter, but if you get in the habit of converting everything to arrays, it's going to sting you eventually.

Of course, you could write a smarter conversion, which didn't have these limitations, but at that point, you are getting no value out of SimpleXML at all, and should just use the lower level XML Parser functions, or the XMLReader class, to create your structure. You still won't have the extra convenience functionality of SimpleXML, but that's your loss.

A quick tip on xpath queries and default namespaces. It looks like the XML-system behind SimpleXML has the same workings as I believe the XML-system .NET uses: when one needs to address something in the default namespace, one will have to declare the namespace using registerXPathNamespace and then use its prefix to address the otherwise in the default namespace living element.

When iterating properties then the extension always iterates overall nodes with that element name. Thus method children() must be called to iterate over subnodes. But also doing the following:foreach ($obj->node_name as $elem) { // do something with $elem}always results in iteration of 'node_name' elements. So no further check is needed to distinguish the number of nodes of that type.

When an elements TEXT data is being accessed through a propertythen the result does not include the TEXT data of subelements.

Known issues============

Due to engine problems it is currently not possible to accessa subelement by index 0: $object->property[0].

Using stuff like: is_object($xml->module->admin) to check if there actually is a node called "admin", doesn't seem to work as expected, since simplexml always returns an object- in that case an empty one - even if a particular node does not exist. For me good old empty() function seems to work just fine in such cases.

[Editor's Note: The SimpleXMLIterator class, however, does implement these methods.]

While SimpleXMLElement claims to be iterable, it does not seem to implement the standard Iterator interface functions like ::next and ::reset properly. Therefore while foreach() works, functions like next(), current(), or each() don't seem to work as you would expect -- the pointer never seems to move or keeps getting reset.